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Tibetan Headwaters of the Yangtze Under Threat

The glaciers which feed the “Yangtze River Source Region” (YRSR) are in the “most sensitive area to global warming” atop the Tibetan Plateau, according to a study led by the Institute of Tibetan Plateau Research. Nearly a quarter of the glacier coverage throughout the headwater region melted from 1970 through the late 2000s, as the Institute of Geographic Sciences and Natural Resources Research found.

Across China “glaciers will play a key role in determining river runoff” in the future, research led by Peking University determined. However, they projected that the nation’s glaciers will “suffer substantial reductions,” with over a quarter of glaciated regions potentially lost by 2050. By the end of the century, in the worst case scenario, as much as 67 percent of China’s glacier volume may completely “disappear.”

China’s water crisis

The nation already faces crippling water crises. As of 2012, two-thirds of China’s 669 cities endured shortages and more than 40 percent of waterways were “severely polluted.”Additionally, 80 percent of its lakes were plagued by eutrophication, and 300 million rural citizens had limited access to safe drinking water. In 2016, China’s Ministry of Water Resources announced that 80 percent of groundwater across the mainland — including the Yangtze, Yellow, Huai and Hai Rivers’ catchments — was “unsafe for human contact.”

To address these issues, China has implemented ambitious water schemes, designed to store and reroute billions of gallons of water from “China’s Water Tower,” the Tibetan Plateau, to thirsty northern provinces. The ‘South-North Water Diversion Project’ and the Three Gorges Dam are two of the best known (and most controversial) projects deployed to address China’s unfolding water crisis.

Asia’s longest river — the Yangtze — sustains over 584 million people, and serves an economic zone which represents nearly 42 percent of China’s GDP (US$4.18 trillion), according to the Hong Kong-based non-profit China Water Risk. The operations within the catchment provide 40 percent of the nation’s electricity and73 percent of its hydropower. The fortunes of China have been built upon the banks of the Yangtze.

The Yangtze’s glaciers

Climate change is having a dramatic effect on the freshwater stores in the Yangtze’s headwater region. In 2007, the State Key Laboratory of Cryospheric Sciences (SKLC) determined that between the 1970s and 1990s the local rate of warming more than doubled, from 0.9°F (0.5°C) per decade to 1.98°F (1.1°C) per decade. According to China’s Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), between 1961–2000 glacier melt contributions averaged 11 percent of the total runoff feeding the Yangtze — over 3 trillion gallons (1.13 billion m3).

By 2013, research led by the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering (Hydro-Lab) indicated that glacier melt now only contributes 5-7 percent of the Yangtze’s annual flow.

Chuancheng Zhao of Lanzhou University, and his colleagues, predicted that temperatures in the YRSR will have increased 5.4°F (3°C) between by the end of the 21st Century. This would result in temperatures 9.18°F (5.1°C) above those observed in the 1970s. This pessimistic projection exceeded by Steve Birkinshaw of Newcastle University and his team in 2016. Their models predicted that if business continues as usual, the region could face a temperature increase of “more than (7.2°F) 4°C” by 2070, compared with pre-2010 conditions.

This would be catastrophic for the YRSR’s glaciers, with severe consequences for all downstream inhabitants and operations. Li Xin of CAREERI projected that across China “glacier runoff will increase continuously from 2000 to 2030,” but will begin to decline after reaching ‘peak water’ by 2030.

Shen Yongping and his colleagues project that, if temperatures rise 5.4°F (3°C) by 2100 as Zhao suggests, “glaciers less than [2.5 miles] 4 km in length in the YRSR would disappear entirely, resulting in a decrease of 60 percent or more in the total area of glacier cover in the region.”

During periods of reduced overall runoff, glacier melt has historically remained constant, or increased, being a staple source for the Yangtze. In the 1990s, total runoff (from all sources) into the Yangtze declined 13.9 percent, according to the SKLC. During this period, 17 percent of the Yangtze’s waters were sourced from glaciers, as glacier melt contributions increased over 15 percent.

There are 753 glaciers in the YRSR, identified through the Chinese Glacier Inventory. The greatest concentrations are located in the Tanggula Mountain Range, which delineates over 370 miles (600 km) of the Qinghai-Tibetan border.

Changes in the Tanggula Mountains

Combined, Tanggula’s glaciers span an area larger than Dallas, Texas — over 102,100 hectares (1,021 km2). The westernmost glaciers surround a 21,722 ft (6,621 m) peak named Geladaindong. Six of the largest glaciers, each expanding over 3,000 hectares (30 km2), radiate outwards from the mountain.

Overall, the 40 glaciers of Geladaindong lost almost 12 percent of their areal extent between 1977 and 2009 — 12,600 hectares (126 km2) — coinciding with a 2.52°F (1.4°C) rise in temperature.

The “most important glacier in the region” is Jianggendiru, the symbolic source of the Yangtze discovered in 1976. Gao Shengyi of the Changjiang Spatial Information Technology Engineering Company accorded the glacier this title in a 2014 study. It is comprised of two ice streams, the north and south, which have been in decline for at least 32 years at an annual rate of 50 ft (15 m) and 68 ft (21 m) respectively.

Despite Gao’s et al. insistence for focus on Jianggendiru, the most catastrophic change has taken place at Gangjiaquba Glacier. Gangjiaquba flows east, and is a source glacier of the Tongtian River, via the Ga’er River. Seventy percent of the glaciers in the YRSR feed into the Tongtian, which accounts for 60 percent of water in the upper Yangtze.

A comparison of satellite images from June 1973 (middle of the melt season) and February 2016 (post-winter maximum extent) reveal that the snout of the glacier retreated up to 2.6 miles (4.2 km). Inferences from trimlines (‘tidemarks’ indicating the glacier’s former extent) on the valley sides, cross-referenced with Landsat satellite imagery, indicate that parts of the Gangjiaquba Glacier thinned up to 190 feet (57 m) over 43 years. Gao and his colleagues calculated Gangjiaquba retreated 330 ft (100 m) per year, on average.

Within the Tanggula Mountain Range, CAREERI project glacial melt will increase up to 30 percent over the coming 34 years (compared to 1961–2000 average). More than 10 percent of the region’s ice will likely disappear, reducing its areal extent by 11,850 hectares (118.5 km2) — twice the size of Manhattan.

In the short term, increased glacier melt will be a boon for hydropower, drought-stricken agricultural lands and towns, thirsty industries, and the like. However, the post-2030 “tipping point” brought about by ‘peak water,’ coinciding with peak population, has even propagandistic mouthpieces, like China Daily, sounding the alarm. (GlacierHub)